1. Field of the Invention
The invention relates to digital storage and display means for generating video signals.
2. Prior Art
Interfacing a digital processor or computer with a raster scanned display, such as on a standard television receiver, presents numerous unique design problems. Copending application Ser. No. 780,967, filed March 24, 1977 now U.S. Pat. No. 4,119,955, "Circuit For Display, Such As Video Game Display", assigned to the assignee of this application, describes one circuit for providing such an interface. This circuit permits the display of a plurality of different patterns on a raster scanned, cathode ray tube and includes means for detecting the coincidence of patterns and the coincidence of patterns with a grid. Content addressable memories (CAMs) are employed to compare the horizontal and vertical beam location with desired object locations. When a match occurs, a pattern is read from a memory and used to control the display's beam.
The circuit described in this copending application requires a separate CAM for each object. Thus, where thirty-two objects are displayable, thirty-two CAMs are used. These CAMs require a substantial amount of substrate area, making it difficult to realize, by way of example, a thirty-two object system on a single substrate. As will be described, the present invention permits the display of up to thirty-two objects, however, with fewer than thirty-two CAMs. In the grouped major system described in this application, four objects are located on the display with one CAM.
In the above mentioned copending application, all objects were treated alike. In the present application, minor systems are employed to handle certain objects. The minor systems allow the efficient handling of these objects with a minimum of processor control and with a maximum of display flexibility.